The Earth experiences various seasons primarily due to its axial tilt, which makes winters colder. However, not all planets in the Solar System share this characteristic.
Mercury
With a year lasting only 88 Earth days, all seasons on Mercury are brief. However, the lack of atmosphere (not to mention oceans) to distribute heat evenly leads to significant temperature variations, creating a very harsh environment.
Mercury has a year that lasts only 88 days, with short seasons. (Image: NASA/Wikipedia).
On Earth, seasons occur mainly due to the axial tilt of approximately 23.5 degrees, causing one hemisphere to receive more sunlight than the other during certain periods. This is not the case for Mercury, where the axial tilt is just 2 degrees.
The distance from Mercury to the Sun varies greatly, from 46 million km to 69 million km. Thus, at its closest point in orbit, Mercury receives twice the amount of solar radiation compared to its farthest point. The actual winter on Mercury occurs when the planet is farthest from the Sun. At that time, the midday temperature at the equator is over 150 degrees Celsius lower than when the planet is at its closest point.
However, the most significant temperature change is not seasonal. A day on Mercury lasts 59 Earth days, providing ample time to heat up or cool down. Even during winter, it can be extremely hot in the middle of the day (around 270 degrees Celsius) at the equator, but at night it can plummet to -173 degrees Celsius at the equator, with even colder temperatures near the poles.
Venus
Venus is extremely hot, even in the middle of winter and midnight, with surface temperatures remaining above 438 degrees Celsius.
Mars
Winter on Mars is more similar to Earth than any other planet. A year on the Red Planet is nearly twice as long as an Earth year, and winter lasts about 4 months. The average temperature on Mars is significantly colder. When winter occurs in one hemisphere, the polar ice cap there grows by trapping about a quarter of the atmosphere (mostly CO2) as dry ice, which then shrinks in spring.
On Earth, the influence of seasons is moderated by the oceans, which also act as a massive heat reservoir. In ancient times, this may have also been true for Mars, albeit to a lesser extent. However, Mars no longer has oceans, resulting in a broader temperature range. Mars can be extremely cold in winter, with recorded temperatures dropping to -153 degrees Celsius, and possibly lower, as many landers and rovers cease operation during winter due to a lack of sunlight for battery charging. This has prevented scientists from recording the coldest temperatures.
The polar ice cap on Mars can expand during winter. (Image: NASA/JPL/USGS).
Jupiter
Jupiter does not have distinct seasons. The planet’s axis is tilted only 3 degrees, not significantly more than Mercury. Jupiter’s orbit is also nearly circular, so the amount of sunlight received does not vary significantly. Winter here is similar to all other times of the year.
Saturn
Saturn’s axis is tilted slightly more than Earth’s, at 26.7 degrees. During times not close to the equinox, one hemisphere of Saturn receives slightly more sunlight than the other. However, this does not significantly alter the temperature. Even during hot summers, Saturn is still too far from the Sun to warm up appreciably. The planet’s thick atmosphere helps redistribute large amounts of heat. In the upper atmosphere, temperatures can drop to -191 degrees Celsius during winter.
Uranus
Uranus has an axial tilt of up to 97 degrees. This causes seasons with significant differences in sunlight exposure, with one pole nearly pointing directly at the Sun in summer and nearly turning away in winter. Thus, winter here is very long and dark. Winter is also extremely cold, primarily because the entire planet remains cold, even colder than Neptune despite being closer to the Sun.
Neptune
With an axial tilt of 28.3 degrees, Neptune’s tilt is greater than Earth’s. Its orbit is also quite circular, so like Earth, seasons are determined by which hemisphere receives more sunlight. However, this planet receives only about 0.1% of the sunlight that Earth does. Unlike Uranus, Neptune receives some warmth from its planetary core, but this warmth does not change seasonally, so the cold in winter is not much different from the cold in summer.
